Have a 1994 Ford Ranger I having a problem.

Hi have a 1994 ford ranger I having a problem with the a/c when I bought the truck the high side port was leaking I got the high side port replace not the hose when I refilled the system I put 3 cans of 12oz of r134a before I put in 2 cans of 12oz of r134a the compressor keeps going on and off for 2 seconds a mechianic told me it needs other can of r134a thats where I get 3 cans when I put in the other can the compressor keeps engauge like it should the air inside the truck wasn't ice cold but it was cool just in few mintes the air inside in the truck got hot when I got home the compressor act like it is low the ofrice tube area is frosting over the lines never been off the sitcker under the hood for the a/c says 1lb 6oz please help me on this problem